Peroxide-substituted polysilazanes

Abstract

An uncrosslinked polysilazane containing chemically bound peroxide groups is prepared by reacting a polysilazane and a hydroperoxide at a temperature below the decomposition temperature of the hydroperoxide. A thermoset polymer is formed by heating an uncrosslinked, peroxide-substituted silazane that is also substituted by alkenyl or alkynyl groups at temperatures sufficiently high to decompose the chemically bound peroxide groups to yield a free radical, thereby initiating crosslinking. The crosslinked polysilazanes can be pyrolyzed to form ceramic articles.

What is claimed is: 
     
       1. An uncrosslinked polysilazane comprising silyl peroxide groups having the formula .tbd.SiOOR wherein R is selected from the group consisting of H, substituted or unsubstituted 1-10 carbon alkyl, 2-10 carbon alkenyl, 2-10 carbon alkynyl, aryl, a carboxylic acid and a silyl group. 
     
     
       2. The polysilazane of claim 1 wherein R is a 1-10 carbon alkyl group. 
     
     
       3. The polysilazane of claim 2 wherein the alkyl group is a t-butyl group. 
     
     
       4. The polysilazane of claim 1 wherein the polysilazane also comprises the groups .tbd.SiR 3  wherein R 3  is a 2-10 carbon alkenyl or alkynyl group. 
     
     
       5. The polysilazane of claim 4 wherein R 3  is an alkenyl group. 
     
     
       6. The polysilazane of claim 5 wherein the alkenyl group is a vinyl group. 
     
     
       7. The polysilazane of claim 1 wherein the polysilazane is a liquid. 
     
     
       8. A process for preparing a crosslinked polysilazane comprising heating an uncrosslinked polysilazane comprising silyl peroxide groups .tbd.SiOOR and .tbd.SiR 3  groups, wherein R is selected from the group consisting of H, substituted or unsubstituted 1-10 carbon alkyl, 2-10 carbon alkenyl, 2-10 carbon alkynyl, aryl, a carboxylic acid and a silyl group, and R 3  is a 2-10 carbon alkenyl or alkynyl group to a temperature sufficient to initiate decomposition of the--SiOOR groups of the polysilazane and further initiate crosslinking through the .tbd.SiR 3  groups of the polysilazane. 
     
     
       9. The process of claim 8 wherein R is a 1-10 carbon alkyl group. 
     
     
       10. The process of claim 9 wherein R is a t-butyl group. 
     
     
       11. The process of claim 8 wherein R 3  is the alkenyl group. 
     
     
       12. The process of claim 11 wherein R 3  is a vinyl group. 
     
     
       13. A crosslinked polysilazane prepared by the process of claim 8. 
     
     
       14. The crosslinked polysilazane of claim 13 wherein the polysilazane is a solid. 
     
     
       15. The process of claim 8 wherein a filler is mixed with the uncrosslinked polysilazane prior to heating. 
     
     
       16. The process of claim 15 wherein the filler is silicon nitride. 
     
     
       17. The process of claim 15 wherein the filler is silicon carbide. 
     
     
       18. The process of claim 8 which additionally comprises pyrolyzing the polysilazane after crosslinking, at a temperature and for a time sufficient to form a ceramic article. 
     
     
       19. The process of claim 15 which additionally comprises pyrolyzing the polysilazane after crosslinking, at a temperature and for a time sufficient to form a ceramic article. 
     
     
       20. A ceramic article produced by the process of claim 18. 
     
     
       21. A ceramic article produced by the process of claim 19.